BZOJ 3996 线性代数

最小割。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define maxv 1050
#define maxn 550
#define maxe 2000050
#define inf 1000000007
using namespace std;
int n,b[maxn][maxn],c[maxn],s,t,g[maxv],nume=1,sum=0,dis[maxv],tot[maxv];
struct edge
{
    int v,f,nxt;
}e[maxe];
queue <int> q;
void addedge(int u,int v,int f)
{
    e[++nume].v=v;e[nume].f=f;e[nume].nxt=g[u];g[u]=nume;
    e[++nume].v=u;e[nume].f=0;e[nume].nxt=g[v];g[v]=nume;
}
void build()
{
    for (int i=1;i<=n;i++)
    {
        addedge(s,i,tot[i]);addedge(i,i+n,inf);
        addedge(i+n,t,c[i]);
    }
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++)
            addedge(i+n,j,b[i][j]);
}
bool bfs()
{
    for (int i=s;i<=t;i++) dis[i]=inf;
    dis[s]=0;q.push(s);
    while (!q.empty())
    {
        int head=q.front();q.pop();
        for (int i=g[head];i;i=e[i].nxt)
        {
            int v=e[i].v;
            if (dis[v]>dis[head]+1 && e[i].f>0)
            {
                dis[v]=dis[head]+1;
                q.push(v);
            }
        }
    }
    return dis[t]!=inf;
}
int dinic(int x,int low)
{
    if (x==t) return low;
    int ret=0;
    for (int i=g[x];i && low;i=e[i].nxt)
    {
        int v=e[i].v;
        if (e[i].f>0 && dis[v]==dis[x]+1)
        {
            int dd=dinic(v,min(low,e[i].f));
            low-=dd;ret+=dd;e[i].f-=dd;e[i^1].f+=dd;
        }
    }
    if (!ret) dis[x]=inf;
    return ret;
}
int main()
{
    scanf("%d",&n);s=0;t=2*n+1;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++)
        {
            scanf("%d",&b[i][j]);
            {sum+=b[i][j];tot[i]+=b[i][j];}
        }
    for (int i=1;i<=n;i++) {scanf("%d",&c[i]);}
    build();
    while (bfs())
        sum-=dinic(s,inf);
    printf("%d
",sum);
    return 0;
}